ASML Holding N.V.
Methods and patterning devices and apparatuses for measuring focus performance of a lithographic apparatus, device manufacturing method

Abstract:

Focus metrology patterns and methods are disclosed which do not rely on sub-resolution features. Focus can be measured by measuring asymmetry of the printed pattern (T), or complementary pairs of printed patterns (TN/TM). Asymmetry can be measured by scatterometry. Patterns may be printed using EUV radiation or DUV radiation. A first type of focus metrology pattern comprises first features (422) interleaved with second features (424) A minimum dimension (w1) of each first feature is close to a printing resolution. A maximum dimension (w2) of each second feature in the direction of periodicity is at least twice the minimum dimension of the first features. Each first feature is positioned between two adjacent second features such that a spacing (w1') and its nearest second feature is between one half and twice the minimum dimension of the first features. A second type of focus metrology pattern comprises features (1122, 1124) arranged in pairs.